Toward gene conservation triage: A framework for assessing the relative risk of genetic degradation to forest trees affected by multiple threats

Background/Question/Methods

Changing climate conditions and threats of pest and pathogen infestation will increase the risk that forest trees could experience population-level extirpation or species-level extinction during the next century.   In the face of these challenges, it will be important to safeguard existing adaptedness within species and to create conditions conducive for future evolution. Forest tree species, however, differ in their physiological tolerances, life-history strategies, and population dynamics. These differences could drive wide dissimilarities among species in their potential responses to changing climate conditions and to insect and disease infestations, so diverse management and genetic strategies will be needed to ensure successful regeneration and restoration efforts.  This will be a particular challenge in species-rich regions such as the Southern Appalachian Mountains of the southeastern United States.  To facilitate the effective use of limited resources, we developed a system that ranks the risk of genetic degradation for more than 130 Southern Appalachian tree species. These include high-elevation species endemic to the 22 million hectare region, species with genetically diverse southern populations isolated from large distributions in the northern United States and Canada, and species widespread across the United States but with high-elevation ecotypes in the Southern Appalachians.  Ecological and life-history traits, species-specific projections of climate change pressure, and predictions of pest and pathogen susceptibility were used to rank the predisposition of these forest tree species to genetic degradation.

Results/Conclusions

This approach serves as a tool for planning management activities and conservation efforts, for evaluating species’ genetic resources, and for detecting vulnerabilities. It has the advantage of accounting for multiple threats that may result in the most severe genetic impacts. Only by considering population-level extirpation as a synergistic process of external threats and intrinsic biological traits will we be able to make predictions of risk that approximate reality for most species. Examples of Southern Appalachian forest tree species with high, moderate and low expected risk of genetic degradation will be presented.  Subsequent gene conservation strategies and prospective management tactics applied to those species will be discussed.  The flexibility of this approach allows for its application at multiple scales and across any area for which data exist on the population dynamics and distribution of the species of interest.